Why do jet engines have the swirls on the cones in front?

For lack of technical knowledge on this stuff, I apologize for the vague question words.

I always seem to see large commercial aircraft with those swirls you see popular with hypnotism and such on the turbines. Is there a reason for this, or is it a marketing ploy? And where did it originate?
Update: Reference:
http://t2.gstatic.com/images?q=tbn:8d5ep-sFlWbQGM:http://www.djibnet.com/photo/417698067-jet-engine-optical-illusion.jpg
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